Designing Built-in Test (BIT) or Built-In Self Test (BIST) capabilities into semiconductor devices (i.e. chips) is a well-known technique used to place the circuitry needed to perform critical performance tests directly on the chip rather than off chip. Without the built in test circuitry, external test equipment must be used to perform the various performance tests. Several limitations of using external test equipment include making connections to the on-chip circuitry through a limited number of contact points or pins, requiring expensive test equipment capable of performing RF measurements, and requiring an extended testing time typical of such measurements. On-chip digital or software based mechanisms, which serve to substitute for such external setups, offer significant reduction in testing costs without resulting in a noticeable increase in chip cost.
Manufacturers designing and building products such as communication devices, often design their products to operate in accordance with industry standards. One such standard is the Bluetooth short-range wireless standard. In order to insure conformance with the standard, qualification tests are performed on the products as part of the manufacturing process. Typically, the testing of communication devices requires the device to be connected to one or more pieces of external test equipment that perform a battery of tests to insure compliance with the standard. The test equipment used is typically bulky in size, costly and requires routine maintenance and calibration of its own.
An essential part of the manufacturing process of an RF transceiver is testing the device to ensure compliance with requirements. These requirements may be dictated by customer demands, requirements from the company's marketing department, or an industry standard such as the Bluetooth standard. In order to test the RF portions of a fully integrated RF transceiver chip, special test equipment is typically required that is capable of handling the RF frequencies generated by the chip.
A diagram illustrating a prior art scheme for testing compliance of a transmitter using high cost RF test equipment is shown in FIG. 1. In this typical example, the transmitter, generally referenced 10, is shown comprising an RF modulator 12 connected to a power amplifier 14. The data to be transmitted, either analog or digital, is input to the modulator which generates a transmit signal that is then amplified using a power amplifier before coupling to an antenna (not shown). As part of the manufacturing process, the transmitter circuitry must be tested to ensure compliance with certain performance requirements.
To determine that the power amplifier is operating correctly, the RF output 18 of the transmitter is tested to check whether the appropriate power levels are being generated. Another test checks to make sure the oscillator frequency is within a tolerable range. Such tests are typically performed using high cost RF test equipment 19 which connects to the RF output of the transmitter and may be adapted to control one or more circuit portions within the transmitter via one or more control signals 17.
The RF test equipment needed to guarantee minimum performance of the chip is typically very expensive, driving up the overall cost of manufacturing the chip. In addition, the measurement time required by such external RF capable test equipment is relatively long. A long measurement time limits the throughput of integrated circuit (IC) production and increases the total manufacturing costs.
It is therefore desirable to be able to test the performance of an integrated RF transceiver chip, in particular the power amplifier and oscillator frequency, using very low cost test equipment and which requires short measurement times.